With the advancement of technology, electronic products such as a mobile phone, a computer and a television are increasingly demanding for the properties of waterproofness, sealing, etc. Thus, how to improve the waterproof and sealing properties of the electronic products has become a very important part in their designs.
Taking sound generation devices, speakers which are commonly used in the electronic products, for example, at present, common speakers mainly include moving-coil speakers, magnetic speakers, capacitive speakers, piezoelectric speakers, etc. The moving-coil speakers have the characteristics of relatively simple manufacture, low cost, low-frequency sound generation advantage, etc. A conventional moving-coil speaker, also known as a moving-coil speaker module, usually comprises a speaker module housing and a speaker unit. The speaker module housing comprises an upper housing and a lower housing which are combined together to form a chamber to accommodate the speaker unit.
To improve the strength of the speaker module housing and to reduce the thickness of a speaker module, a metal insert is usually disposed in the position, corresponding to the speaker unit, of the upper housing and/or the lower housing of the speaker module housing, and forms the upper housing and/or the lower housing of the speaker module housing together with a plastic part by injection molding. Since the metal insert and the plastic part are significantly different in material and low in binding force, the plastic part contracts with cold after injection molding and cooling of the two. A portion, in contact with the metal insert, of the plastic part is easy to separate from the metal insert. Consequently, a gap is formed between the metal insert and the plastic part and will deteriorate the waterproof and sealing properties of the speaker module.
Besides, in order to improve the binding force between the metal insert and the plastic part to avoid the gap formed therebetween as much as possible, the length of a portion embedded into the plastic part of the metal insert is usually increased. However, when the upper housing and the lower housing of the speaker module housing are combined by means of ultrasonic sealing (also known as ultrasonic welding), the relatively greater length of the portion embedded into the plastic part of the metal insert will affect transfer of ultrasonic energy to lead to ultrasonic unmelting near the metal insert, greatly reducing the waterproof and sealing properties of the speaker module.